| Abstract: | A marked increase in preglomerular resistance mediated through the renin-angiotensin system has been proposed as the mechanism for the sustained decrease in glomerular filtration rate seen following release of 24-hour ureteral obstruction. The importance of the renin-angiotensin system in mediating this response was evaluated by determining whole kidney and single nephron function following release of 24-hour ureteral obstruction in rats with normal renal renin content and in rats depleted of renal renin by desoxycorticosterone acetate acetate (DOCA) and saline treatment. The DOCA and saline treatment was effective in reducing renal renin content to less than 10% of the normal values. However, when compared to nonobstructed kidneys, both whole kidney filtration rate and single nephron filtration rate were similarly and significantly reduced in both groups following release of 24-hour ureteral obstruction. Single nephron stopflow techniques were used to determine the net hydrostatic force for filtration. The net hydrostatic force for filtration in control nonobstructed nephrons averaged 37.8 +/- 1.1 mm. Hg, but was significantly decreased to 22.5 +/- 2.2 mm. Hg in the normal renin obstructed kidney and to 18.8 +/- 1.0 mm. Hg in the renin-depleted obstructed kidney. It is concluded that the marked depression in glomerular filtration rate seen following release of 24-hour ureteral obstruction is due to increased afferent arteriole resistance and that the renin-angiotensin system is apparently not important in mediating the response. |
